Laser assembly

ABSTRACT

A plurality of disks include solid laserable material and are in parallel spaced apart relation within a transparent tubular enclosure. Spaces between the disks constitute portions of a collant fluid passage within the tubular enclosure. Transparent end members at the opposite ends of the tubular enclosure are located in the path of radiant energy emitted by the laserable material. Coolant fluid passes radially through an exterior sleeve which encircles the end of the tubular enclosure. Sealing means are located between the exterior sleeve and the outside surface of the tubular enclosure. Adjustment means on the exterior sleeve urge a second sealing means against an axially outwardly facing surface of each transparent end member. The inner end portion of each transparent end member confronts the laserable material and has radial dimensions less than the corresponding internal dimensions of the tubular enclosure. A spacer sleeve is telescopically fitted over the inner end portion and extends axially therebeyond to provide a coolant passage space between the inner end portion and the laserable material. The coolant passage also includes a portion formed by an axiallyextending radially-relieved portion of the transparent end member which extends along the transparent end member and inside the spacer sleeve. The outer portion of the transparent member includes a plug portion which conforms to the inside dimensions of the tubular enclosure to reduce the risk of coolant fluid leakage.

United States Patent [1 1 Zitkus LASER ASSEMBLY Wayne J. Zitkus, Toledo,Ohio [73] Assignee: Owens-Illinois, Inc., Toledo, Ohio [22] Filed: Mar.26, 1971 {21] Appl. No.: 128,552

[75] Inventor:

Primary Examiner-Edward S. Bauer Attorney-Richard D. Heberling et al.

[57] ABSTRACT A plurality of disks include solid laserable material andare in parallel spaced apart relation within a transparent tubularenclosure. Spaces between the disks constitute portions of a collantfluid passage within the tubular enclosure.

[ 3,750,050 1 July 31,1973

Transparent end members at the opposite ends of the tubular enclosureare located in the path of radiant energy emitted by the laserablematerial. Coolant fluid passes radially through an exterior sleeve whichencircles the end of the tubular enclosure. Sealing means are locatedbetween the exterior sleeve and the outside surface of the tubularenclosure. Adjustment means on the exterior sleeve urge a second sealingmeans against an axially outwardly facing surface of each transparentend member.

The inner end portion of each transparent end member confronts thelaserable material and has radial dimensions less than the correspondinginternal dimensions of the tubular enclosure. A spacer sleeve istelescopically fitted over the inner end portion and extends axiallytherebeyond to provide a coolant passage space between the inner endportion and the laserable material. The coolant passage also includes aportion formed by an axially-extending radially-relieved portion of thetransparent end member which extends along the transparent end memberand inside the spacer sleeve. The outer portion of the transparentmember includes a plug portion which conforms to the inside dimensionsof the tubular enclosure to reducethe risk of coolant fluid leakage.

9 Claims, 4 Drawing Figures PATENIEDJUL 3 I 1915 POWER SOURCE FIG. I

HE AT EXCHANGER FIG. I

LASER ASSEMBLY tion of the transparent end member, often called areadout prism," which lies in the path of radiant energy emitted by thelaserable material. One approach has been to provide a radially-relievedportion which extends for the total length of the readout prism with nostructure being provided in the readout prism assembly for maintaining aspacing for a coolant passage between the readout prism and thelaserable material. Another approach to this problem has involved areadout prism which is frictionally retained on the tubular enclosure bya compressed sealing element which engages the interior wall of thetubular enclosure. This previous structure has also included a spacersleeve which is telescoped over a reduced diameter inner end portion ofthe readout prism, with axial coolant passages being provided on theexterior surface of the spacer sleeve. A modification of this latterdevice has involved attachment of the retaining members for the readoutprism to the cavity or housing which encloses a flash lamp and thelaserable material. In either instance, the machining of the spacersleeve is difficult and it has displayed a tendency to crack whensubjected to the high temperatures normally encountered in apparatus ofthis type.

The present invention involves improvements to the end structure forfluid-cooled laser assemblies.

One aspect of the invention involves the manner of connecting thetransparent end member or readout prism to the tubular body whichencloses the laserable material. An exterior sleeve encircles an endportion of the tubular enclosure and is provided with two differenttypes of sealing means. One sealing means prevents coolant fluid leakagebetween the exterior sleeve and the external wall of the tubular body,and the second sealing means acts against an axially facing outersurface of the transparent member. Means on the exterior sleeve areprovided for urging the second sealing means against the axially facingouter surface.

Another aspect of the invention pertains to the construction of thetransparent end member itself, wherein it includes a plug portion whichconforms to the inside dimensions of the tubular body. A radiallyrelieved portion of the transparent end member is located inwardly ofthe plug portion to form a space within the tubular body to permit thepassage of coolant fluid.

Another portion of the invention involves the relationship between thetransparent end member and the spacer sleeve which is telescoped overthe inner end portion of the transparent member to maintain thelaserable material spaced from'the transparent member. Specifically,this aspect of the invention involves a coolant passage which extendsalong the readout prism member and is located inside the spacer sleeve.

Still another feature of the invention involves the method of assemblingthe individual elements of a laser assembly by telescoping a spacersleeve over a reduced end portion of a transparent end member,positioning a key which rotationally fixes the spacer sleeve to thetransparent end member, and inserting these elements together into thetubular enclosure so as to confine the key radially within the tubularenclosure and axially between the spacer sleeve and the readout prismmember.

Another phase of the invention pertains to structure wherein a spacersleeve is telescoped over the inner end portion of a transparent endmember. The transparent end member has a planar abutment surface whichextends radially inwardly of the spacer sleeve to providesurface-to-surface abutment between the transparent end member and thespacer sleeve.

The features of the invention outlined above, either alone or inconjunction with each other, have been found to simplify theconstruction of laser assemblies, reduce the cost of their manufactureand provide reliable performance under normal operating conditions.

While the invention may take many forms, a preferred embodiment thereofis shown in the accompanying drawings wherein FIG. 1 is a diagrammaticshowing of the general organization of a laser which embodies thepresent invention;

FIG. 2 is an exploded view showing the transparent readout prism member,spacer sleeve and representative disks which include the solid laserablematerial;

FIG. 3 is a sectional view through the apparatus to show the coolantpassage; and

FIG. 4 is a sectional view as seen along the line 4-4 in FIG. 3.

A typical laser construction is shown in diagrammatic form in FIG. 1wherein an interiorly-reflective laser cavity" or housing 2 encloses aflash tube 4 which furnishes the excitation energy and a transparenttubular enclosure 6 which encloses the laserable material.

At each end of the tubular enclosure 6, there is an end sealing assemblygenerally designated 8 which includes an exterior sleeve 10 whichencircles the end portion of the tubular enclosure 6. Retaining meansformed by a split ring assembly having upper elements 12 and lowerelements 14 are bolted together and engage both the tubular enclosure 6and the exterior sleeve 10 in a manner best shown in FIG. 3. Extendingfrom the ends of the laser assembly is an end surface 16 of thetransparent end member which transmits the laser-emitted radiant energyfrom the tubular enclosure 6.

A power source 5 energizes the flash lamp 4. A plurality of such linearflash lamps or a single helical flash lamp may alternatively be used.Since the walls of the tubular enclosure 6 are transparent and thelaserable material is located therewithin, the energy emitted by theflash lamp 4 strikes the laserable material within the tubular enclosure6 and creates the laser action in a manner well known in the art.

Fluid conduits 18 and 20 are attached to ports in the exterior sleeves10 in order to provide a closed path for the coolant fluid. Acirculating pump 24 moves the coolant fluid through conduit 18 into theexterior sleeve 10, and thence coolant fluid is passed through a conduit20 to a heat exchanger 22. Coolant fluids are preferably liquid and maybe water, heavy water, ben zene, Freon or other suitable materials.

Referring to FIG. 2, it will be noted that the readout prism assembly.includes an end member 26 and a spacer sleeve 28. The end member 26includes an inner end portion 30 which has a reduced transverse crosssection with respect to the inside diameter of the tubular enclosure 6.The inner end surface 32 of the member 26 confronts the disks 34, eachof which includes a peripheral band of cladding glass 36 and a centralportion 38 of laserable neodymium-doped ED-2 glass Nd. The claddingglass may be ED-S glass. Both types of glass are available from theassignee hereof. Energy emitted by the laserable material 38 will bedirected through the transparent end member 26 and will be emittedthrough its end surface 16.

The transparent end member 26 has a medial portion 40 and an outerportion which includes both a plug portion 42 and a reduced end portion44. The portions 30, 40, 42 and 44 are transversely circular during anintermediate stage of their manufacture. A cut is made in the member 26so as to provide a radially relieved surface 46 which extends both alongthe medial portion 40 and the inner end portion 30. This surface 46 maybe planar, but preferably it is arcuate, being generated about a linewhich lies parallel to the longitudinal axis of the end member 26.

The spacer sleeve 28 is a cylindrical tubular member with an insidediameter which is substantially the same as the outside diameter of theinner end portion 30 of end member 26. The outside diameters of thespacer sleeve 28 and plug portion 42 of the end member 26 are bothsubstantially equal to the inside diameter of the tubular enclosuremember 6. The outer end surface 48 of the spacer sleeve 28 abuts againsta shoulder 50 on the transparent readout prism member 26. The innersurface of the spacer sleeve 28 is at an acute angle with respect to thecentral axis thereof and includes a pair of arcuate portions 52 and 54which abut against the cladding material of the adjacent disk 34.

The inner end surface of the spacer sleeve is axially relieved at 56 and57 to maximize the area of the disk 34 which is contacted by the fluidcoolant. It is preferable that the surfaces 32, 52 and 54 lie atBrewsters angle with respect to the central axis of the apparatus.However, other angles may be adopted and, if appropriate coolantmaterials are found, these surfaces may lie normal to the axis of theassembly.

The axial position of the spacer sleeve 28 on the transparent end member26 is determined by the abutment of the outer end of the spacer sleeveagainst the shoulder 50 of the transparent end member 26. In order toensure that there is a surface-to-surface abutment in this area, thesurface 50 extends radially inwardly beyond the outer surface of theinner end portion 30 to form a peripheral groove 51. The same machiningstep which forms the surface 50 also creates the groove 51. Theresulting structure avoids the presence of a fillet at the juncture ofthe shoulder 50 and the inner end portion 30 which would interfere withthe desired abutting relationship.

It is desirable to prevent relative rotation between the readout prismmember 26 and the spacer sleeve 28. In the disclosed and preferredembodiment, such rotational movement is prevented by means of a solid.polytetrafluoroethylene key 74 which, as shown in FIG. 3 is received ina keyway cut in the adjacent external surfaces of the spacer sleeve 28and the medial portion of the member 26. The keyway is simultaneouslymachined in both parts while they are held together by wax. The key isthen placed in the keyway and the entire assembly is inserted into thetubular enclosure 6 to confine the key 74 radially within the tubularenclosure 6 and axially between the member 26 and the spacer sleeve 28.

The manner of attaching the readout prism assembly to the tubularenclosure body is best shown in FIG. 3 where it will be noted that theexterior sleeve 10 has a pair of internal circumferential grooves 58which receive a pair of axially spaced resilient O-ring sealing elements60. These elements 60 form a seal between the exterior sleeve 10 and theouter surface of the tubular enclosure 6. Located between the O-rings isanother circumferential groove 62 which is in communication with anopening 64 in the wall of the tubular enclosure 6. A fitting 66 providesan opening which extends through the sleeve 10 between the sealingelements 60 to provide fluid communication to the coolant passages inthe apparatus.

Coolant entering the apparatus through the fitting 66 will pass firstthrough the internal groove portion 62 and then through an opening 64 inthe wall of the tubular glass enclosure. The coolant then enters theaxial passage 68 which exists by virtue of the radially relieved portionof the transparent end member 26. The coolant progresses then into thepassage 70, which lies between the spacer sleeve 28 and the inner endportion 30 of the prism 26. As seen in FIG. 3, the spacer sleeve 28extends inwardly beyond the surface 32 of the readout prism 26 so thatthere is a space 72 located between the member 26 and the first of thedisks 34 which contain the laserable material. The construction of thedisks 34 is such that a coolant fluid will pursue a serpentine orsinuous path as it progresses along the length of the laser assembly.

In the preferred embodiment shown in FIG. 3, the exterior sleeve 10 isheld at a fixed axial position on the tubular enclosure 6 by the splitring retaining members 12 and 14 which have inwardly-facing grooves 76and 78 which receive outwardly-directed projections 80 and 82 on theexternal sleeve. The retainers l2 and 14 are received in a externalcircumferential groove 84 cut 0 into the tubular enclosure 6. In effect,the provision of the groove 84 creates a radial projection 86 whichholds the sleeve 10 at a fixed axial position. Radial projections mayalternatively be formed by external flange or flared tapered portions atthe end of the tubular enclosure 6.

In addition to the seal provided by the O-rings 60 against the exteriorsurface of the tubular enclosure 6, there is a second sealing meansassociated with the external sleeve 10 which acts against an outwardlyaxially facing surface 88 of the transparent end member 26. Thisstructure involves the O-ring seal 90 which is radially confined by theinwardly-directed flange portion 92 of the sleeve 10. On its interiorside, the O-ring 90 lies against the cylindrical outer surface of thereduced end portion 44 of the end member 26. The inner side of the seal90 contacts the surface 88, while its outer side is confronted by anaxially-movable annular member 94.

In order to compress the sealing member 90, the sleeve 10 is providedwith an adjustable means for urging the O-ring against the surface 88.This involves an exteriorly-threaded member 96 which is threadedlyengaged with interior threads on the sleeve 10. The member 96 confrontsthe outer surface of the annular member 94 so that rotation of themember 96 moves member 94 inwardly to apply compressive forces againstthe O-ring 90 and all other elements within the tubular enclosure 6. Itis possible to use an adjustable threaded connection between theexterior sleeve and a member attached to the tubular enclosure 6; or,tensioned members may be used to interconnect both of the exteriorsleeves 10. The effective length of the tensioned members may be variedto provide the adjustment means on the sleeve for urging a seal againstthe outer end surface of the transparent end members.

In a typical laser assembly which utilized the principles of theinvention, the tubular enclosure 6 had a overall length of about 22inches, an outside diameter of about 1.25 inches and an inside diameterof about 0.877 inch. It was formed of non-laserable glass available fromthe assignee hereof under the designation ED-4. Its arcuate surfaceswere made transparent by finish-polishing, and its end surfaces wereprovided with a fine ground (220 diamond) finish. The transparent endmembers were made of a non-laserable fine anneal ED-4 glass made by theassignee hereof. Their overall length was about 4 inches and theirmaximum outside diameter was about 0.874 inches. Each arcuateradially-relieved surface 46 had its center of curvature located about0.25 inch from the longitudinal centerline of the transparent end member26, and had a radius of curvature of 17/32 inch. The inner end surfacewas at an angle of 52 39.5 to the longitudinal centerline of member 26.The spacer sleeve 28 was also made of ED-4 glass and had its inclinedsurfaces 52 and 54 lying at an angle of 48 27.7 with'respect to itslongitudinal centerline.

The exterior sleeve assembly including members 10, 12 and 96 were formedof rhodium plated brass; whereas the annular gland member 94 is made ofrhodium plated 303 stainless steel. The O-rings were resilient and madeof silicone rubber and before being inserted in the apparatus had insidediameters less than those of the interiorly-confining members andoutside diameters greater than those of the exteriorly-confiningmembers.

Those skilled in the art will realize that the disclosed features of theinvention are not limited only to glass lasers or spaced-disk lasers andmay take many forms which differ in appearance from the disclosedpreferred embodiments. The scope of the invention is not limited to thedisclosed structure, but encompasses other methods and structures whichadopt the principles outlined in the claims which follow.

I claim:

1. A laser assembly comprising,

an imperforate tubular body,

solid laserable body located within said tubular body,

said tubular body and said laserable body being constructed and arrangedto form a coolant passage located interiorly of the tubular body in heatconducting relation to the laserable body whereby heat exchange fluidmay remove heat from the laserable body,

a transparent member of solid material located within the tubular bodyat at least one end thereof in the path of radiant energy emitted by thelaserable body, said transparent member having an inner end portionconfronting the laserable body and an outer end portion which includesan outer surface transverse to the axis of said laser assembly,

an exterior sleeve encircling an end portion of the tubular body andhaving a means through which said heat exchange fluid communicates withsaid interiorly located coolant passage,

means to hold said exterior sleeve at a fixed axial position withrespect to the tubular body,

first sealing means preventing fluid leakage between the exterior sleeveand the outside surface of the tubular body,

second sealing means being axially movable to sealingly engage the outersurface of the transparent member to said exterior sleeve, and

adjustment means on the exterior sleeve for urging the second sealingmeans axially against the outer surface of the transparent member toprevent the loss of coolant fluid from the tubular body.

2. The apparatus of claim 1 wherein the tubular body has an externalradial projection, retaining means attached to said exterior sleeve andengaged against said projection for holding the exterior sleeve at afixed axial position with respect to the tubular body.

3. The apparatus of claim 1 wherein the first sealing means includes apair of axially spaced sealing elements, said tubular body having afirst radial opening located between the sealing elements and incommunication with the coolant passage, and a second opening extendingthrough the exterior sleeve between the sealing elements to providefluid communication to the coolant passage.

4. The apparatus of claim 3 wherein the tubular body has an externalradial projection, retaining means attached to said exterior sleeve andengaged against said projection for holding the exterior sleeve at afixed axial position with respect to the tubular body.

5. The apparatus of claim 3 wherein the transparent member is in closeengagement with the inside surface of the tubular body, said transparentmember being radially relieved along a side thereof to form a portion ofthe coolant passage which is aligned with said first opening.

6. The apparatus of claim 5 wherein the laserable body includes aplurality of parallel spaced disks, said inner end portion of thetransparent member having a reduced transverse cross section, saidradially relieved side of the transparent member extending axially alongthe inner end portion, and a spacer sleeve telescoped over the inner endportion and extending axially therebeyond to contact a first said diskto maintain a space which forms a portion of the coolant passage betweenthe first disk and the inner end portion.

7. The apparatus of claim 6 wherein the disks form an acute angle withrespect to the longitudinal axis of the tubular body.

8. The apparatus of claim 6 wherein the disks lie at Brewsters anglewith respect to the longitudinal axis of the tubular body.

9. The apparatus of claim 8 wherein the inner end portion has an innerend surface which confronts the disks and is inclined with respect tothe longitudinal axis of the tubular body at a different acute anglethan said disks.

1. A laser assembly comprising, an imperforate tubular body, solidlaserable body located within said tubular body, said tubular body andsaid laserable body being constructed and arranged to form a coolantpassage located interiorly of the tubular body in heat conductingrelation to the laserable body whereby heat exchange fluid may removeheat from the laserable body, a transparent member of solid materiallocated within the tubular body at at least one end thereof in the pathof radiant energy emitted by the laserable body, said transparent memberhaving an inner end portion confronting the laserable body and an outerend portion which includes an outer surface transverse to the axis ofsaid laser assembly, an exterior sleeve encircling an end portion of thetubular body and having a means through which said heat exchange fluidcommunicates with said interiorly located coolant passage, means to holdsaid exterior sleeve at a fixed axial position with respect to thetubular body, first sealing means preventing fluid leakage between theexterior sleeve and the outside surface of the tubular body, secondsealing means being axially movable to sealingly engage the outersurface of the transparent member to said exterior sleeve, andadjustment means on the exterior sleeve for urging the second sealingmeans axially against the outer surface of the transparent member toprevent the loss of coolant fluid from the tubular body.
 2. Theapparatus of claim 1 wherein the tubular body has an external radialprojection, retaining means attached To said exterior sleeve and engagedagainst said projection for holding the exterior sleeve at a fixed axialposition with respect to the tubular body.
 3. The apparatus of claim 1wherein the first sealing means includes a pair of axially spacedsealing elements, said tubular body having a first radial openinglocated between the sealing elements and in communication with thecoolant passage, and a second opening extending through the exteriorsleeve between the sealing elements to provide fluid communication tothe coolant passage.
 4. The apparatus of claim 3 wherein the tubularbody has an external radial projection, retaining means attached to saidexterior sleeve and engaged against said projection for holding theexterior sleeve at a fixed axial position with respect to the tubularbody.
 5. The apparatus of claim 3 wherein the transparent member is inclose engagement with the inside surface of the tubular body, saidtransparent member being radially relieved along a side thereof to forma portion of the coolant passage which is aligned with said firstopening.
 6. The apparatus of claim 5 wherein the laserable body includesa plurality of parallel spaced disks, said inner end portion of thetransparent member having a reduced transverse cross section, saidradially relieved side of the transparent member extending axially alongthe inner end portion, and a spacer sleeve telescoped over the inner endportion and extending axially therebeyond to contact a first said diskto maintain a space which forms a portion of the coolant passage betweenthe first disk and the inner end portion.
 7. The apparatus of claim 6wherein the disks form an acute angle with respect to the longitudinalaxis of the tubular body.
 8. The apparatus of claim 6 wherein the diskslie at Brewster''s angle with respect to the longitudinal axis of thetubular body.
 9. The apparatus of claim 8 wherein the inner end portionhas an inner end surface which confronts the disks and is inclined withrespect to the longitudinal axis of the tubular body at a differentacute angle than said disks.